Optical Coherence Tomography (OCT) is a promising diagnostic imaging technology that utilizes advanced photonics and fiber optics to obtain cross-sectional tomographic images on a microscopic resolution scale. The technology has the potential to dramatically change the way physicians, researchers and scientists see and understand the human body in order to better diagnose and treat disease. OCT combines the principles of ultrasound with the imaging performance of a microscope and a form factor that is familiar to clinicians.
Whereas ultrasound produces images from backscattered sound “echoes,” OCT uses infrared light waves that reflect off the internal microstructure within the biological tissues. The frequencies and bandwidths of infrared light are orders of magnitude higher than medical ultrasound signals resulting in greatly increased image resolution; about 8-25 times greater than ultrasound or x-ray based modalities. OCT uses coherence-gating to detect singly-scattered photons thereby permitting tomographic imaging similar to ultrasound or computed tomography (X-ray), but at much higher resolution. While standard electronic techniques are adequate for processing ultrasonic echoes that travel at the speed of sound, interferometric techniques are required to extract the reflected optical signals from the light used in OCT. The output, measured by an interferometer, is computer processed to produce high-resolution, real time, cross sectional or 3-dimensional images of the tissue. This powerful technology provides in situ images of tissues at near histological resolution without the need for excision or processing of the specimen.
For example, imaging of coronary arteries by intravascular OCT may reveal the location of a stenosis, the presence of vulnerable plaques, or the type of atherosclerotic plaque. This information helps cardiologists to choose which treatment would best serve the patient—drug therapy (e.g., cholesterol-lowering medication), a catheter-based therapy like angioplastry and stenting, or an invasive surgical procedure like coronary bypass surgery.
One of the fundamental limitations of cardiovascular OCT is that it cannot image through blood because the components of red blood cells strongly scatter the near-infrared light, making image reconstruction impossible. As a result, there is a need for systems, methods, and apparatus that facilitate and detect blood clearing in a lumen. The aspects and embodiments of the invention discussed below addresses this need.